Pre-fabricated tracks are nice because they have the raised area at the bottom of the track. This minimizes glass to track surface contact and also allows for dust and substrate to be channeled away. Both of those make for a much smoother running track.
Both Rockler.com and Woodcraft.com sell plastic track. The "tan" product at woodcraft is actually orange. See the picture of my Bearded Cage below.
Rockler's sells a product that is brown and I much prefer that track.
I believe both of them sell hardwood tracks with the same raised area in the bottom.
So if you want to make your own track I recommend doing so with a router to mimic the raised track bottom. You would have to make 4 passes total to accomplish that.
I don't know what radius bit you would need. I think it would be pretty easy to figure out.
